The present invention pertains to a locking device for two components of a height- and tilt-adjustable motor vehicle steering column. The components are displaceable relative to one another, wherein one component is fixed on a bracket stationarily connected to the body of the vehicle and the other component is part of a steering column housing accommodating the steering column, with at least two toothed surfaces, which are fixed on the components that are displaceable in relation to one another and can be brought into engagement with one another.
Locking devices having the features of this type are used in the automobile industry in both passenger cars and trucks for the temporary fixation of a steering column. The fixation is set by the driver beforehand with respect to height and tilt corresponding to his personal needs. The fixation of the housing accommodating the steering column with the bracket that is a rigid part of the body is to be designed such that no relative movements will occur between the steering column housing and the body in the locked state of the device even in the case of an accident despite strong forces acting on the steering column, because such movements would compromise the function of air bag passenger protection systems which are now commonly used. Locking devices with positive-locking elements, especially with toothed racks designed as toothed surfaces which engage one another, offer a reliable and inexpensive possibility of providing the necessary holding forces. However, the use of pairs of toothed racks is associated with the system-inherent drawback that there are positions between the steering column housing and the bracket, that is a rigid part of the body, in which the toothed racks arranged on the respective components are in a xe2x80x9chead-over-headxe2x80x9d position in relation to one another. Even though the locking device can be fixed by the driver under certain circumstances in this special position, there is no real locking of the steering column housing and the bracket (i.e., that is a rigid part of the body) in relation to one another, so that a danger to the driver due to an uncontrolled relative movement between the components of the steering column in the case of an accident cannot be ruled out.
The object of the present invention is therefore to improve a locking device of this type such that the head-over-head position of the tooth heads in the toothed racks used in the locking devices is reliably ruled out under all circumstances.
This object is accomplished according to the present invention by the toothed surfaces each having at least one row of teeth with a plurality of teeth arranged next to one another, wherein the free tips of the teeth of two rows, which free tips face one another, are mutually repelled by magnetic forces.
It is achieved due to this design according to the present invention with a magnetic force free tip repulsion means that if two individual teeth of the toothed surfaces that are to be brought into engagement with one another stand one over the over, the teeth of one toothed rack will automatically slide off due to a lateral displacing movement into the spaces between the teeth of the opposite toothed rack, which opposite toothed rack is fixed on the stationary body bracket. A stable tooth-over-tooth position of the toothed racks or toothed surfaces located opposite one another is thus ruled out by the repulsion between the mutually opposite tooth tips, which repulsion is brought about by the magnetic forces.
Special embodiments of the subject of the present invention with locking device for two components of a height- and tilt-adjustable motor vehicle steering column having a magnetic force free tip repulsion means are described herein.
The tooth tips of the mutually opposite rows of teeth may have the same north or south polarity as needed, the only thing decisive for the function according to the present invention being that the tooth tips polarized in the same direction shall mutually repel one another due to the repulsive effect of magnet poles polarized in the same sense, which is known from magnetism.
In addition, it may be advantageous for the tooth bottoms located between the free tips of the two tooth rows, which free tips face one another, to have a polarity that is magnetically opposite to the polarity of the free tips of the teeth. The engagement effect of the two rows of teeth located one over another is supported by magnetic attracting forces due to this measure according to the present invention. This is due to the fact that after the mutually repelling tooth tips of the mutually opposite rows of teeth slide off into an adjacent tooth space, attracting forces between the tooth tips of opposite polarizations and the tooth bottoms located opposite them support the engagement effect of the two rows of teeth If the tooth tips of the rows of teeth have a magnetic north polarity, the opposite polarization with a south polarity leads to an attracting force of these opposite magnetic poles during the engagement of the rows of teeth.
Moreover, it may be useful to separate the functions of tooth engagement of the rows of teeth and the resulting provision of the required holding forces from the function of preventing the tooth heads from being located one over another in a simple and inexpensive manner within the framework of the separation of the functions. This can be accomplished according to the present invention in such a way that two magnetic strips provided with individual magnets are provided one over another adjacent to the tooth surfaces that can be brought into engagement with one another on the mobile component and on the stationary bracket for the steering column on the body, the individual magnets being arranged at spaced locations at a distance corresponding to half the tooth pitch of the teeth of the toothed racks, which said teeth are arranged next to one another, and the individual magnets being polarized in the same direction. This special embodiment of the subject of the present invention can be realized in a particularly inexpensive manner. The magnetic strips arranged next to the toothed racks may be equipped with commercially available small magnets. The only thing to be observed in arranging the individual magnets is that the individual magnets of the two mutually opposite magnetic strips shall be located with their equal polarization one over another at the moment at which the toothed racks are also in a head-over-head position. The individual magnets will repel one another in this position due to their equal polarization and thus bring about at the same time an offset of the toothed racks due to a lateral relative movement, so that a head-over-head position of the tooth tips is no longer given. The spaced arrangement of the individual magnets within the magnetic strips makes possible the engagement of the individual magnets just as well as the engagement of the rows of teeth during the locking operation, so that a reliable engagement of the teeth of the toothed racks with one another is guaranteed after the conclusion of the locking operation.
The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this disclosure. For a better understanding of the invention, its operating advantages and specific objects attained by its uses, reference is made to the accompanying drawings and descriptive matter in which a preferred embodiment of the invention is illustrated.